High-speed document processing systems, such as those utilized for sorting of bank checks and financial documents are capable of moving and processing large volumes of documents at high speeds, while performing multiple and interrelated operations upon each document as documents travel through feeders and document processors. Such operations may include, for example, printing upon documents, image capturing, and other processes and document manipulations. While processing large volumes of documents, it is important that each individual document be transported and processed singly, and that documents remain in the order and sequence in which they are processed. Should two or more documents be accidentally fed and processed together, subsequent processing time and manual effort and time are required to detect such errors. Therefore, measures have been implemented to insure that document feeding and separating measures always feed documents one at a time through document processing systems.
While document feeders have been developed to minimize the feeding of more than one document at a time, a problem arises when the unavoidable circumstance occurs when more than one document is fed at a time. A need has thus arisen for a system to detect multiple feeding of documents so that appropriate operations may be performed by the system, either to prevent the multiple fed documents from reaching a document handling station, or to allow the document handling station to reject the multiple fed documents.